Sealing and Transversal Cutting Device for Loose Product Packaging Systems

ABSTRACT

Herein described is a device for sealing and cutting film in packaging systems for loose product, comprising transversal rotating shafts synchronised with each other, to which a couple of pincers is engaged comprising sealing and cutting means. Said pincers are connected to mechanisms comprising lower prestretching plates and upper prestretching plates forced in predefined positions by springs that react to a set almost circular path that brings the two pincers into contact one in front of the other so that the upper ones hold back the loose product and the lower ones carry out a prestretching of the film, so as to prepare the film for sealing and cutting without any interpositioning of loose product.

The present invention refers to a sealing and transversal cutting device for loose product packaging systems.

The operations of filling and closing plastic bags containing loose products such as crisps, biscuits, salted snacks or similar, are extremely critical.

In conventional machines the sealing and cutting of the plastic film come about by means of a couple of pincers rotating in opposite senses that support sealing means and a blade. When said pincers meet themselves during rotation, they press the film together, seal it and cut it.

A common problem of these machines is that in order to prevent the product that is being packaged from remaining caught between the pincers it is necessary to interrupt the flow of the product.

The numerous interruptions that follow during the delivery of the product being packaged causes a limitation of the production and the frequent blocking of the product inside the tubular film from which the single bags are formed, in particular if the product is light-weight in comparison to the volume, such as crisps, pop-corn, . . . etc.

There are machines, for example as described in U.S. Pat. No. 5,540,035, that have a stage of pre-accumulation prior to the sealing and cutting stage, which blocks the flow of the product being packaged towards the abovementioned sealing and cutting stage by means of pincers moved by levers that clamp the passage channel of the film. In this case a batch is created upstream of the clamp as the machine that feeds the product being packaged does not stop. Once the film has been sealed and cut in further downstream area, the clamping pincers open and the product “falls” downwards where it again accumulates.

The quantity of product that accumulates in the sealing and cutting stage must be such that, when the pincers clamp the film, it prevents the product from being caught between them. The pincers of the pre-accumulation stage must therefore act at the right moment so as to avoid excessive passage of the product. The same flow of product delivered by the machine must be set with precision.

The disadvantage of this system consists in having to use practically two devices that have to be synchronised with absolute precision.

For example in EP-1319600, EP-0666215 and EP-1362790, unique devices are known that enable both the block of the flow of product being packaged and the sealing and cutting operations. In said devices the block is determined by a system of arms connected rigidly to the pincers, which have end bars that clamp the film upstream and downstream of the pincers. Said rigidity can create problems in the phases of setting the device. The blocking bars must be such that they clamp the film, which is usually a few millimetres thick. It is extremely easy to make positioning error thus enabling the product being packaged to “invade” the sealing and cutting area. It can also happen that there is interference between said bars, with the risk of seriously damaging the device.

Said system of rigid arms also causes problems of overall dimensions during the rotation of the pincers when they occupy non-working positions.

Object of the present invention is to produce a film sealing and cutting device that comprises a flexible mechanism, has limited overall dimensions and is easy to use, that is capable of preventing the product being packaged from being caught between the sealing and cutting pincers.

In accordance with the invention this object is achieved with a film sealing and cutting device for packaging systems for loose products, comprising transversal rotating shafts synchronised with each other, to which a couple of pincers is engaged comprising sealing and cutting means, characterised in that said pincers are connected to mechanisms comprising lower prestretching plates and upper prestretching plates actuated in predefined positions by springs that react to a preset almost circular path that brings the two pincers in contact one in front of the other so that the upper ones hold back the loose product and the lower ones carry out the prestretching of the film, so as to prepare the film for sealing and cutting without any interpositioning of loose product.

The presence of the springs gives flexibility to the mechanism guaranteeing the opening of the plates and thus the prestretching of the film in function of the position of the mechanisms themselves. The plates are thus mobile in relation to the pincers. In addition when they are not in the working position the plates tend to “wind” the pincers, so that the rotating mechanism has extremely reduced overall dimensions.

The characteristics of the present invention will be made even more evident by the following detailed description of an embodiment thereof illustrated as non-limiting example in the enclosed drawings, in which:

FIG. 1 shows a side view of the device according to the present invention with the pincers and the relative mechanisms in a horizontal position, opposed to each other;

FIG. 2 shows a side view of the device according to the present invention with pincers and mechanisms in a vertical position orientated upwards;

FIG. 3 shows a side view of the device in a position successive to that of FIG. 2;

FIG. 4 shows a side view of the device in a position successive to that of FIG. 3 when the plates start to open;

FIG. 5 shows a side view of the device in a position successive to that of FIG. 4;

FIG. 6 shows a side view of the device in a position successive to that of FIG. 5 in which the opening of the plates has been completed and the pincers clamp the film;

FIG. 7 shows a side view of the device in a position successive to that of FIG. 6 in which the mechanisms are horizontal one in front of the other with the cutting means in the phase of cutting the film;

FIG. 8 shows a side view of the device in a position successive to that of FIG. 7 after the film has been cut;

FIG. 9 shows a side view of the device in a position successive to that of FIG. 8;

FIG. 10 shows a side view of the device in a position successive to that of FIG. 9;

FIG. 11 shows a side view of the device in a position successive to that of FIG. 10 in which the mechanisms are in a vertical position orientated downwards with the plates completely closed;

FIG. 12 shows a plan view from above of the device in the same position as FIG. 1;

FIG. 13 shows a plan view from above of the device in the same position as FIG. 7;

FIG. 14 shows a section view according to the line XIV-XIV of FIG. 12;

FIG. 15 shows an enlarged partial view of FIG. 1;

FIG. 16 shows an enlarged partial view of FIG. 1.

FIGS. 12-14 show a first transversal rotating shaft 1 and a second transversal rotating shaft 2 synchronised with each other, controlled by a motor that is not shown by means of a transmission 24 comprising a wheel 25 surrounded by a belt 40, a first toothed wheel 26 and a second toothed wheel 27.

A frame 22 supports said shafts 1-2 through bearings 23 suitable for ensuring the rotation in relation to the same frame 22.

Shims 5 connect the shafts 1-2, on which they are joined, to transversal support bodies 3-4.

Rotating mechanisms 6-7, which are supported by said transversal bodies 3-4 respectively, comprise each one a mobile lower body 8 and a mobile upper body 9 fitted with small wheels 51, springs 10-11 and pincers 32 and 34 which in the work position (FIGS. 1-11) clamp and then release a plastic film 100 suitable for collecting product to be packaged 101. The springs 10-11 have a first extremity fixed to supports 60-61 of the mobile bodies 8-9 by means of pins 45-46, and a second extremity connected to mobile bodies 8-9 by means of pins 70-71.

Between the two rotating shafts 1-2 guide cams 50 are positioned for the preflattening connected to the frame 22.

The mobile bodies 8-9 are free to rotate around the pins 13-14 in one with the supports 60-61.

The transversal body 3 (highlighted in FIG. 16) also supports a blade 15 which is movable between a work position and a rest position by means of guide cams 16 of the blade 15 joined on the shaft 1, which in certain angular positions (FIG. 7) interfere with bearings 17 causing a body 18 to advance in one with the blade 15 that is forced to remain in the work position by transversal springs 19 housed partly in the transversal body 3 and partly in said body 18.

The blade 15 moves through a fissure 31 obtained in the pincers 32, and when it is in the work position (FIG. 7) the extremity of the blade 15 partially occupies a fissure 33 obtained in the pincers 34.

The mobile bodies 8-9 also support respectively lower prestretching plates 28 and upper prestretching plates 29, as the lower plates 28 are fitted with feet 30.

Small wheels 20, associated to the transversal bodies 3-4, engage recesses 21 enabling the mechanisms 6-7 to follow an almost circular path. Lower joints 54 and lower joints 55 permit the connection of all the circular sections 56 with the straight sections 57.

As regards to the operation, a motor that is not shown in the Figures moves the belt 40 that makes the shaft 1 rotate. The interlocking between the toothed wheels 26-27 also enables the rotation of the second shaft 2.

Considering that of FIG. 1 as a starting position of the device, the two shafts 1-2 rotate in opposite senses thus permitting the two mechanisms 6-7 to meet themselves where the plastic film 100 flows vertically in the straight section 57 of the path of the pincers 32, 34.

The prestretching plates 28, 29 in the FIGS. 1-11 and 15 are drawn with a thicker line than that of the other details drawn so as to highlight the relative motion.

It can be seen in FIG. 4 that the lower plates 28 meet themselves thereby prestretching the film, while the plates 29 are still slightly distanced. The pressure that is generated at the point of contact of the plates 28, due to the track set by the recess 21 that progressively becomes vertically straight by means of the joint 55, causes the same plates 28 to open. The feet applied on the lower plates 28 serve to make the interaction with the film 100 “softer” as it could otherwise be damaged. The mobile bodies 8 rotate around the pins 13 moving towards the pins 70 that lengthen the springs 10 against the force of reaction carried out by the same springs 10 that tend to close the plates 28.

The upper plates 29 also start to open as the small wheels 51 meet the cams 50 inducing the rotation of the bodies 9 around the pins 14 and the movement downwards of the pins 71 that thus lengthen the springs 11. So as the upper plates 29 open, it is necessary for the pressure deriving from the interaction between the small wheel 51 and the cams 50 to be greater than the counter force of the springs 11. The plates 29 do not come into contact with each other but they are however close enough as not to permit the product being packaged 101, that continues falling from above, to occupy the area between the two pincers 32, 34. The product being packaged 101 accumulates above the plates 29 until the mechanisms 6-7 detach from each other.

As explained above, one of the advantages of this device is exactly that of enabling the sealing and cutting operations without interrupting the feeding of the product being packaged 101 that thus results continuous.

When the path becomes perfectly straight and vertical the movement of the plates 28-29 ends and the pincers 32 and 34 meet and clamp the film 100 (FIG. 6).

FIG. 7 shows the position in which the sealing and cutting comes about. In this position, in fact, sealing means 102, 104 associated to the front of the pincers 32, 34 clamp the film 100 between them, making the seal of the opposite flaps of the same. In addition the cams 16 come into contact with the bearings 17 causing the body 18 and thus the blade 15 that cuts the film 100 to move ahead. The pressure between the cams 16 and bearings 17 must be such to overcome the contrary force induced by the springs 19.

When the cut has been made the mechanisms (6-7) move downwards until they meet the lower joint 54 (FIG. 9) that leads to the progressive disengagement of the lower plates 28 (FIG. 10) which thanks to the action of the springs 10 return to the initial closed position. In this phase there is the “fall” of the bag below 105 filled with product 101.

At the end of the lower joint 54, when the interaction between the small wheels 51 and the cams 50 does not come about, the upper plates 29 also return to the initial closed position in virtue of the force carried out by the springs 11 (FIG. 11). At the moment in which the upper plates 29 start moving away, the product being packaged 101 starts to fall again inside the film 100 under the sealing and cutting area. 

1. Device for sealing and cutting film in packaging systems for loose product, comprising rotating transversal shafts (1-2) synchronised with each other, to which a couple of pincers (32, 34) is engaged comprising sealing and cutting means (15), characterised in that said pincers (32, 34) are connected to mechanisms (6, 7) comprising lower prestretching plates (28) and upper prestretching plates (29) forced in predefined positions by springs (10, 11) that react to a set almost circular path that brings the two pincers (32, 34) into contact one in front of the other so that the upper ones hold back the loose product (101) and the lower ones carry out a prestretching of the film (100), so as to prepare the film (100) for sealing and cutting without any interposition of loose product.
 2. Device according to claim 1, characterised in that said springs (10, 11) are operatively interposed between transversal bodies (3, 4) of said pincers (32, 34) and lower and upper mobile bodies (8-9) supporting said prestretching plates (28, 29).
 3. Device according to claim 1, characterised in that it comprises a cam (50) for guiding the prestretching with which small wheels (51) belonging to the upper mobile bodies (9) interact enabling the opening of the upper plate (29).
 4. Device according to claim 1, characterised in that said shafts (1, 2) are connected to a motion transmission (24).
 5. Device according to claim 1, characterised in that said pincers (32, 34) present a fissure (31, 33) transversal to the film.
 6. Device according to claim 5, characterised in that said cutting means consist of a mobile blade (15) inside the fissure (31) of one (32) of said pincers (32, 34).
 7. Device according to claim 1, characterised in that it comprises a cam (16) for guiding the blade (15) interacting in certain angular positions with a body (18) to which the blade (15) is engaged.
 8. Device according to claim 1, characterised in that said lower plate (28) has a prestretching foot (30).
 9. Device according to claim 1, characterised in that it comprises rigid connection shims (5) between the rotating shafts (1, 2) and the transversal support bodies (3, 4). 